Question

Hemoglobin - Short Essay Question

1. On a molecular level explain what happens when the structure of hemoglobin changes from the low to the high affinity form. What role does O2 play in the process? What happens at the site of O2 Binding?

Answer 1

ANSWER:-Hemoglobin exists in 2 forms, the taut form (T) and the relaxed form (R). This structural change to the taut form leads to low-affinity hemoglobin whereas the relaxed form leads to a high-affinity form of hemoglobin, with respect to oxygen binding .hemoglobin has four units all are bind together ,due to this tension is generated between them, the oxidation state of Fe in the any monomer unit of hemoglobin is +2 and Fe has 5 binding sites with 4 porphyrin ring and 1 histidine ring and due to this high spin Fe does not able to fit in porphyrin ring so the structure of monomer unit of hemoglobin look like domb shape.

when a oxygen molecule is bind with a monomer unit of hemoglobin in superoxide form,then oxidation state of Fe is changes to +2 high spin to +2 low spin due to pairing of electron and the size of Fe becomes smaller than previous and now it gets fitted in porphyrin ring and its geometry becomes planar due to this shape the nitrogen of histidine becomes closer to Fe ,due to closeness of nitrogen the interaction between four units is decrease and they get in relaxed form,

ROLE OF O₂ IN THE PROCESS:- oxygen increases the rate of binding in the monomer unit of hemoglobin

at the binding site of O₂ Fe changes high spin to low spin state  ,becomes planar and changes tens to  relaxed form.